1. Field of the Invention
The present invention relates to a magnetic coil having three terminals for energization, a magnetic contactor using said magnetic coil, and a manufacturing method for said magnetic coil.
2. Description of the Background Art
FIG. 12 illustrates the arrangement of a magnetic coil and its peripheral elements in a conventional magnetic contactor which allows the magnetic coil to be energized via three terminal blocks. FIG. 13 illustrates a sectional view of the conventional magnetic contactor in FIG. 12. In these drawings, a magnetic coil 1, a coil frame 2 of the magnetic coil, a first terminal groove 2a formed in the coil frame 2, a second terminal groove 2b positioned opposite to the first terminal groove 2a, a winding 3 provided on the coil frame 2, a first coil terminal 4 press-fitted in the first terminal groove 2a of the coil frame 2, and a first terminal portion provided at the front end of the first coil terminal 4 and constituting an external wiring portion are shown. A start-of-winding tying portion 4b projects from the side face of the first coil terminal 4 and a second coil terminal 5 is disposed opposite to the first coil terminal 4 and press-fitted in the second terminal groove 2b of the coil frame 2. A second terminal portion 5a is provided at the front end of the second coil terminal 5, positioned opposite to the first terminal portion 4a, and constitutes an external wiring portion. An end-of-winding tying portion 5b projects from the side face of the second coil terminal 5, and a third terminal 5c is provided at the other end of the second coil terminal 5, positioned diagonally opposite to the first terminal portion 4a, and has a third terminal portion which constitutes an external wiring portion.
A case 6 accommodates the magnetic coil 1, supports the coil frame 2, and supports the terminal portions of the first coil terminal 4 and the second coil terminal 5. Panel installation holes 6a are disposed diagonally in the bottom surface of the case. A first terminal supporter 6b, a second terminal supporter 6c and a third terminal supporter 6d, support the terminal portions of the first terminal supporter 4 and the second terminal supporter 5. An E-shaped fixed core 7 has a central pole which is inserted into the magnetic coil 1 to support the coil frame 2 from the bottom surface. A movable core 8 is opposed to the fixed core 7 and is moved vertically by magnetic force generated by the magnetic coil 1. A contact support frame 9 is fixed to the movable core 8 and movable contacts 10 are switched on/off by the operation of the contact support frame 9. Fixed contacts 11 are opposed to the movable contacts 10, and a housing 12 secures the fixed contacts 11 and supports the contact support frame 9. A first terminal block 13 is constituted by the first terminal portion 4a and the first terminal supporter 6b. A second terminal block 14 is constituted by the second terminal portion 5b and the second terminal supporter 6c, and a third terminal block is constituted by the third terminal portion and the third terminal supporter 6d.
FIG. 14 illustrates a perspective view of the conventional magnetic coil showing the details of the coil frame 2 and the second coil terminal 5 in the arrangement of the magnetic contactor in FIG. 12, wherein a first press-fitting projection 21 is formed in a substantially L shape by cutting part of the second coil terminal 5. A second press-fitting projection 22 is opposed to the first press-fitting projection 21 and is formed in an oppositely substantially L shape to the first press-fitting projection 21. Catch projections 23 are formed by extrusion and a cross groove 24 is formed between the thin-wall plates of the coil frame 2 in the second terminal groove 2b of the coil frame 2. A first press-fitting groove 25 is formed perpendicularly to the cross groove 24. A second press-fitting groove 26 is opposed to the first press-fitting groove 25, and catch holes 27 are formed so as to pierce the upper thin-wall plate of the cross groove 24.
FIG. 15 is a perspective view showing the terminal block section of the conventional magnetic contactor disclosed in Japanese Laid-Open Patent Publication No. HEI 2-284325, wherein parts 21-26 correspond to those in the conventional art in FIG. 14.
The conventional magnetic contactor having three coil terminals is arranged as described above, and the first terminal block 13 and the second terminal block 14 are disposed on the power supply side of the magnetic contactor, spaced a sufficiently insulated distance away from the wiring to the power supply side of the fixed contacts 11, and wired unidirectionally. The third terminal block 15 is disposed diagonally opposite to the first terminal block 13 and is employed when wiring is employed on both the power supply side and load side of the magnetic contactor. When the magnetic contactor is wired, the first terminal block 13 and the second terminal block 14 can be wired, and at the same time, the first terminal block 13 and the third terminal block 15 can also be wired to allow a worker to select the terminal blocks according to the ease of wiring. When a thermal relay or the like has been fitted to the load side of the magnetic contactor, that terminal block which interferes with wiring can be avoided.
When the magnetic contactor according to the conventional art in FIG. 12 is installed to a panel, the magnetic contactor is fixed to the panel before the second terminal block 14 is wired since the panel installation hole 6a is arranged under the second terminal block 14, and is accessed with a screwdriver obliquely from the top to avoid the second terminal block 14.
The magnetic coil 1 is assembled with consideration given to winding workability. The first coil terminal 4 and the second coil terminal 5 integrated with the third coil terminal 5c are fitted to the coil frame 2, the start point of the winding 2 is soldered to the start-of-winding tying portion 4b, the winding is subsequently wound by a winder, and finally the winding end point is soldered to the end-of-winding tying portion 5b.
The first coil terminal 4 and the second coil terminal 5 are fitted to the coil frame 2 as shown in FIG. 14 (only terminal 5 is illustrated). The first press-fitting projection 21 and the second press-fitting projection 22 are inserted into the first press-fitting groove 25 and the second press-fitting groove 26, and the opposed inner faces of the first press-fitting projection 21 and the second press-fitting projection 22 are pressed against and fixed to the wall surfaces in the second terminal groove 2b. Further, the catch projections 23 and the catch holes 27 engage to prevent removal after press-fitting. When press-fitting fixture and engagement are executed simultaneously as shown in FIG. 15, the permanent engagement effect can be increased.
In the process of winding the magnetic coil 1 of said magnetic contactor, as shown in FIG. 17, a winder provided with a series of winding shafts, each of which is inserted into the center hole of a coil frame 2, is employed, and the winding shafts are rotated synchronously to rotate the coil frames 2, thereby winding the magnetic coils.
However, whereas the conventional magnetic coil 1 is improved in wiring performance because it has three terminals, projecting from both ends of the coil frame 2, the winding shaft-to-winding shaft distance which is equal to the value of [(the maximum radius 28).times.2+(the clearance 29)], required for the winder, i.e., the dimensions of each winding station, must be increased as compared to that for generally used magnetic coils on which two coil terminals project in only one direction, whereby the winding work space is increased.
The magnetic contactor is desired to be compact to reduce the size of the control box in which the contactors are arranged and to make the control box more compact and slim.
However, since the winding of the conventional magnetic coil 1 is done after the fitting of the first coil terminal 4 and the second coil terminal 5 integrated with the third terminal 5c between the flanges of the coil frame 2, winding is not easily carried out. If the first coil terminal 4, the second coil terminal 5 and the third coil terminal 5c are located higher than the flanges of the coil frame 2, this poses a problem of electrical insulation between the terminal blocks and a main circuit or an auxiliary circuit located above them. Hence, the first coil terminal 4, the second coil terminal 5 and the third coil terminal 5c are projected in both directions and secured to the flange height positions of the coil frame 2.
For this reason, attempts to make the magnetic contactor more compact are limited by the insulation relationship between said coil terminal blocks and the main circuit or auxiliary circuit located above them, whereby the magnetic contactor cannot be made sufficiently compact.
Also, according to the usual form of magnetic contactor, e.g., when a thermal relay is fitted beforehand in close contact with the load side of the magnetic contactor, the terminal block located on the thermal relay side cannot be used due to interference with the thermal relay. In such a case, three terminal blocks are not required and a magnetic contactor having only two coil terminals projecting in only one direction is desirable in view of product costs and the like.
However, since the conventional magnetic coil 1 has three terminals projecting from both ends of the coil frame 2 for improvement in wiring performance, the third terminal will be wasted when said magnetic coil is employed as above.
Further, in the conventional magnetic contactor, the forces applied to the device during manufacture vary in direction, particularly with respect to the second terminal portion 5a, the third terminal portion and the end-of-winding tying portion 5b in the case of the second coil terminal 5, so that all portions cannot always be fixed sufficiently, whereby the outside of the first press-fitting projection 21 and the second press-fitting projection 22 are easily affected by vibration and wiring-time fastening.